The present invention relates to a device for automatic injection of a product in a very safe way, especially for self-injection.
In this application, the device has a longitudinal axis which is the main axis of the constitutive parts of said device. The distal end of a component or of a device is to be understood as meaning the end furthest from the user's hand and the proximal end is to be understood as meaning the end closest to the user's hand. Likewise, in this application, the “distal direction” is to be understood as meaning the direction of injection, and the “proximal direction” is to be understood as meaning the opposite direction to the direction of injection.
Some illnesses necessitate regular injections of drugs or products, for instance on a daily basis. In order to simplify the treatment, some self-injectors have been provided in order to allow the patient to perform the injection on its own.
Of course, since the patient is usually neither a nurse nor an educated person in medical devices, such self-injectors must prove to be very simple to use and also very safe. In particular, the insertion of the needle must be performed at the right depth, the correct dose of product must be injected, that is to say a complete injection must be performed, and the injector must be deactivated after use before it is disposed of. Preferably, the needle should not be exposed, before and after use, in order to prevent any accidental needlestick injury.
The injection devices of the prior art are usually provided with needle shields that are made of rubber or elastomeric material. A drawback of these devices is that the sharp needle, embedded into the rubber shield, may create a core of rubber if rotated when removed. Then, this rubber core, located into the needle internal diameter, may then block the needle and prevent the drug to be injected or may be injected into the patient's skin together with the drug upon activation of the injection device.
It would therefore be of interest to provide an injection device having an appropriate needle shield that does not jeopardize the quality of the injection when it is removed from the injection device before use.
Some injection devices of the prior art comprise a deshielder which is initially coupled to said needle shield and removably assembled to the distal part of a housing of the injection device. The deshielder is intended to be removed from said housing prior to use of said device, thereby also removing the needle shield. To avoid the creation of the rubber core, the deshielder and the housing are usually provided with connecting means designed to make it impossible to rotate the deshielder with respect to the housing, which would entail the rotation of the needle shield with respect to the needle and, consequently, the creation of such a rubber core. In other words, the only possibility for the patient to remove the needle shield, by means of the deshielder, is to pull the deshielder axially. This arrangement has a number of drawbacks.
First of all, the straight pulling movement is quite difficult to perform, especially for elder or arm and hand impaired people, because this movement requires a certain force and uses both hands and forearms.
Moreover, in the first instance, many users may tend to turn the deshielder instead of pulling it axially, since the removal of caps is generally performed through a rotational movement. Consequently, these users may be confused when realizing that the deshielder cannot be removed in this way, and may take time to try to pull the deshielder axially in order to remove it.
Consequently, there is a need for self-injection devices provided with a needle shield and a deshielder that could be removed by a rotational movement with no risk to create a rubber core in the needle.
Besides, there is also a need for such a self-injection device that would also allow a patient used to known devices to remove the deshielder by pulling it axially.